Possible convertion commands:
convert -size 300x300 <IMAGE_NAME>.jpg -monochrome <IMAGE_NAME>.tiff
for f in *.jpg; do convert -resize 15% -size 300x300 -monochrome "$f" "<PATH_TO_FOLDER_WITH_FILES>/${f%%.*}.tiff"; done
magick convert <IMAGE_NAME>.tiff -resize 15% <IMAGE_NAME>.tiff